Currently-available e-mail systems used with the Internet accept any message directed to the recipient's address. An exception to receipt of such messages is a blocking device that will selectively block a specific address or series of addresses, perhaps identified by a particular domain name. To utilize this type of blocking, one must identify the unwanted sender and enter its identify in a database. However, this still permits the receipt of other, heretofore unidentified, but unauthorized messages. A scheme that would prevent the receipt of such messages without having to first identify them would be highly desirable.